1. Field of the Invention
The invention relates to a computer device and, more particularly, to a computer device with a built-in universal serial bus (USB) device.
2. Background of the Invention
With the progress of the digital science and technology, the personal computer becomes an essential electronic product for people. Therefore, many consumer electronic products such as digital cameras and mobile phones provide interfaces for being connected with personal computers to allow users to increase the functions of the products via the strong functions of the personal computers. To achieve this objective easily and conveniently, a plug and play (PNP) USB interface is introduced.
To popularize the USB, USB Implementers Forum (USBIF) establishes many related specifications to make the USB available for many electronic devices under the same specification. In the aspect of the operating power, since many integrated circuits are designed to operate at 5 volts when the specification is established, the interface operating power of the USB device is also defined to be 5 volts.
However, no power supply circuit supplying 5-volt output power exists in the personal computer system. Thus, some voltage regulators are designed to solve the problem.
FIG. 1 is a block diagram showing a conventional connected built-in USB digital camera. The digital camera 110 includes an image sensor 111, a USB bridge 112, a voltage regulator 113 and a lens 114. The USB bridge 112 is coupled to a controller 121 on a conventional motherboard via a USB B1, and it also is coupled to the image sensor 111 and the voltage regulator 113. In addition, the image sensor 111 may be disposed on the transmitting path of light passing the lens 114 to capture outside images.
In the conventional technology, since the image sensor 111 (such as a complementary metal oxide semiconductor (CMOS) sensor of a camera in a notebook computer) in the digital camera 110 and the USB bridge 112 need 3.3-volt operating power to operate, a power supply circuit 124 and a power supply circuit 125 are used to provide 19-volt operating power and 3.3-volt operating power, respectively. Furthermore, as stated above, the interface operating power of the USB device is defined to be 5 volts. Therefore, in the conventional technology, a voltage regulator 123 only may be used to reduce the 19-volt power generated by the power supply circuit 124 to 5-volt interface voltage, and then a voltage regulator 113 adjusts the 5-volt interface voltage to be 3.3-volt operating power of the image sensor 111 and the USB bridge 112.
Although the power supply circuit 125 which may provide 3.3-volt power is disposed in the computer system, it cannot be used directly, and the voltage regulator 123 and the voltage regulator 14 are used additionally, which is a waste of costs. Moreover, when the voltage regulator converts the voltage, it consumes power and wastes electricity.